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Use algebra and identities in the text to simplify the expression. Assume all denominators are nonzero. $$\frac{5 \cos t}{\sin ^{2} t} \cdot \frac{\sin ^{2} t-\sin t \cos t}{\sin ^{2} t-\cos ^{2} t}$$

Short Answer

Expert verified
Question: Simplify the expression given below: $$\frac{5 \cos t}{\sin ^{2} t} \cdot \frac{\sin ^{2} t-\sin t \cos t}{\sin ^{2} t-\cos ^{2} t}$$ Answer: The simplified expression is: $$\frac{5\cos t \sin t (\sin t - \cos t)}{1 - 2\cos^2 t}$$

Step by step solution

01

Identify common factors to cancel

In order to cancel any common factors, observe that there is a \(\sin^2 t\) in the denominator of the first fraction and in the numerator of the second fraction. Cancel out the common factor \(\sin^2 t\). $$\frac{5 \cos t}{\sin ^{2} t} \cdot \frac{\sin ^{2} t-\sin t \cos t}{\sin ^{2} t-\cos ^{2} t} = \frac{5 \cos t}{1} \cdot \frac{(\sin ^{2} t-\sin t \cos t)}{\sin ^{2} t-\cos ^{2} t}$$
02

Factor out the expression in the numerator of the second fraction

In the numerator of the second fraction, notice that there is a common factor of \(\sin t\). Factor out this to simplify the expression. $$\frac{5 \cos t}{1} \cdot \frac{(\sin ^{2} t-\sin t \cos t)}{\sin ^{2} t-\cos ^{2} t} = \frac{5 \cos t}{1} \cdot \frac{\sin t(\sin t - \cos t)}{\sin ^{2} t-\cos ^{2} t} $$
03

Use the Pythagorean identity

We can use the Pythagorean identity \(\sin^2 t + \cos^2 t = 1\) to simplify the remaining denominator. Since the denominator is \(\sin^2 t - \cos^2 t\), we can rewrite it as \((1 - \cos^2 t) - \cos^2 t\). $$\frac{5 \cos t}{1} \cdot \frac{\sin t(\sin t - \cos t)}{\sin ^{2} t-\cos ^{2} t} = \frac{5 \cos t}{1} \cdot \frac{\sin t(\sin t - \cos t)}{(1 - \cos^2 t) - \cos^2 t} $$
04

Simplify the denominator expression

Now we can simplify the denominator expression by combining the terms involving \(\cos^2 t\). $$\frac{5 \cos t}{1} \cdot \frac{\sin t(\sin t - \cos t)}{(1 - \cos^2 t) - \cos^2 t} = \frac{5 \cos t}{1} \cdot \frac{\sin t(\sin t - \cos t)}{1 - 2\cos^2 t} $$
05

Express the final simplified expression

After simplifying the expression, our final result will be: $$\frac{5 \cos t}{1} \cdot \frac{\sin t(\sin t - \cos t)}{1 - 2\cos^2 t} = \frac{5\cos t \sin t (\sin t - \cos t)}{1 - 2\cos^2 t}$$

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Trigonometric Identities
Trigonometric identities are equations that hold true for all values of the variables involved and provide a way to express one trigonometric function in terms of others. These identities are not only fundamental in the study of trigonometry but also form the backbone for simplifying complex trigonometric expressions. For example, in the provided exercise, if we recognize a pattern or a trigonometric identity, we can replace the complex parts of an expression with simpler forms that lead us closer to the solution.

Commonly used identities include reciprocal identities, quotient identities, and Pythagorean identities, among others. Pythagorean identities, such as \(\sin^2 t + \cos^2 t = 1\) or its rearranged forms, are often used to simplify expressions involving squares of sine and cosine functions, which is precisely what was necessary to simplify the denominator in the exercise.
Pythagorean Identity
The Pythagorean identity is particularly useful in transforming and simplifying trigonometric equations. It is derived from the Pythagorean Theorem related to the sides of a right triangle and is given as \(\sin^2 t + \cos^2 t = 1\). This identity implies that the sum of the squares of sine and cosine of an angle equals one, and it can be manipulated to express one function in terms of the other.

By using this identity, mathematicians can simplify expressions that involve squared trigonometric functions. As illustrated in the exercise, we can replace \(\sin^2 t\) with \(1 - \cos^2 t\) or vice versa, which helps in reducing the overall complexity of the trigonometric expression being simplified.
Algebraic Simplification
Algebraic simplification involves various techniques used to make expressions more manageable and straightforward. These techniques include factoring, expanding, combining like terms, and canceling common factors among other operations. The aim of algebraic simplification is to transform a complex expression into an equivalent but simpler form that is easier to work with or understand. In the exercise, the process of canceling out the common factor \(\sin^2 t\) between the numerator and the denominator, and combining like terms involving \(\cos^2 t\), are classic examples of algebraic simplification. Each step reduces the complexity and moves towards a simpler final expression.
Factoring Expressions
Factoring is a powerful algebraic tool used to break down expressions into products of simpler factors. It is particularly handy when simplifying fractions, solving equations, and finding common factors or roots. When you factor an expression, you're essentially looking for components that, when multiplied together, will reconstruct the original expression. This is visible in the exercise where \(\sin t\) is factored out from the numerator of the second fraction.

Knowing how to factor expressions confidently requires practice and recognition of common patterns, such as the difference of squares or trinomials. Factoring not only simplifies calculations but also lays the groundwork for further algebraic manipulation that can lead to solving complex problems efficiently.

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Most popular questions from this chapter

Use algebra and identities in the text to simplify the expression. Assume all denominators are nonzero. $$(\sin t) /(\tan t)$$

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